1. Field of the Invention
The present invention relates to a siroco fan, and more particularly to a siroco fan employed in a window type air conditioner, which does not increase the noise of operation while maintaining the quantity of the blowing air, even when the rotational speed of the siroco fan is increased.
2. Description of the Related Art
In general, a window type air conditioner has a casing 10, which contains a compressor 12 for compressing refrigerant, a condenser 14 for condensing the refrigerant compressed by the compressor 12 to lower the temperature of the refrigerant, and an evaporator 16 for performing a heat exchange operation by means of the refrigerant cooled by the condenser 14.
The interior of the window type air conditioner is divided into an indoor section and an outdoor section by a partitioning panel 18. In the indoor section are disposed the evaporator 16 and a siroco fan 20 for circulating indoor air through the siroco fan 20, while in the outdoor section are disposed the compressor 12, the condenser 14, and an axial-flow fan 30 for cooling the condenser 14 by means of outdoor air.
The siroco fan 20 is disposed behind a bell mouth 11 in the casing 10. The siroco fan 20 includes a shroud 21 and a plurality of blades 22 disposed at the shroud 21 which are spaced apart at regular intervals, as shown in FIG. 2. In order to reduce the dimension and manufacturing cost of the air conditioner, the siroco fan 20 and the axial-flow fan 30 are disposed in such a manner as to be operated together by a single driving motor 40. In this case, a rotation shaft 41 of the driving motor 40 has opposite ends assembled with the siroco fan 20 and the axial-flow fan 30, respectively.
In the window-type air conditioner as described above, warm indoor air is cooled while being introduced through the evaporator 16 and the bell mouth 11 in the casing 10. The introduced air is compressed by the blades 22 of the siroco fan 20 and then discharged out of the casing 10, so that the indoor air is properly cooled or air-conditioned. In this case, the refrigerant warmed after exchanging heat with the warm air at the evaporator 16 is cooled by outdoor air introduced into the outdoor section by means of the operation of the axial-flow fan 30, while passing through the condenser 14. The refrigerant is then circulated while performing its heat-exchange operation.
The blowing characteristic of the siroco fan 20 is influenced by such features as the number of blades 22, the blade span B, the inner diameter d1 of the siroco fan 20, which is the distance between the opposing inner ends of the blades 22, and the outer diameter d2 of the siroco fan 20, which is the distance between the opposing outer ends of the blades 22.
The number of the blades 22 is determined by the ratio between the chord L1, which is the distance between the inner end and the outer end of each blade 22, and the pitch L2, which is the distance between the adjacent two outer ends of the blades 22, as shown in FIG. 3a. 
Furthermore, the blowing characteristic of the siroco fan 20 is also influenced by the shape of the blades 22, which is determined in consideration of the leading edge angle xcex2, the trailing edge angle xcex1, the blade thickness T, and the largest camber position P, as shown in FIG. 3b. The trailing edge angle xcex1 is a factor causing an increase in the static pressure, and the fan can perform superior blowing capability when the trailing edge angel xcex1 is in a range between 145xc2x0 and 165xc2x0.
In the meantime, the axial-flow fan 30 has a smaller quantity of blowing air in comparison with the siroco fan 20, based on the same motor output. Accordingly, in the case where the siroco fan 20 in the indoor section rotates together with the axial-flow fan 30 in the outdoor section by utilizing a single driving motor outputs of the siroco fan and the axial flow fan will be different. In consideration of the above difference in the quantity of blowing air from the respective fans, the rotational speed of the driving motor 40 should be set above a predetermined reference, so that the axial-flow fan 30 having the smaller blowing capability can perform the necessary blowing capability.
Accordingly, in the window type air conditioner containing a conventional siroco fan as described above, since the rotating speed of the siroco fan is very high, the quantity of the indoor air blown by the siroco fan exceeds the cooling capability of the evaporator, making the operation of the air conditioner ineffective and inefficient
In the prior art, in order to overcome the above problem of ineffective operation of the air conditioner, the outer diameter d2 of the siroco fan 20 between the opposed outer ends of the blades 22 is reduced, or the blade span B is reduced.
However, according to these two ways of either reducing the outer diameter or the blade span, although the quantity of the blowing air is reduced, the modified construction of the blade 22 generates increased noise, thereby causing a deterioration in the marketability of the air conditioner.
Accordingly, the present invention has been made in an effort to solve the problems occurring in the related art, and thus it is an object of the present invention to provide a siroco fan in a window-type air conditioner which does not increase the noise of operation while maintaning the quantity of the blowing air, even when the rotational speed of the siroco fan is increased.
In accordance with one aspect of the present invention, there is provided a siroco fan for a window-type air conditioner, the siroco fan comprising a shroud and a plurality of blades disposed at the shroud and spaced apart in regular intervals, wherein each of the blades has a trailing edge angle of 125xc2x0 to 137xc2x0, a leading edge angle of 58xc2x0 to 63xc2x0, a chord-to-pitch ratio of 0.75 to 0.85, an inner diameter-to-outer diameter ratio of 0.82 to 0.86, and a maximum camber position of 0.3 to 0.4 of a chord length of the blade. Preferably, the siroco fan has forty to fifty blades.